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Anthropogenic Lakes-the reservoirs
The reservoir, as its name suggests, is a "warehouse" to store water. It is a special kind of storing water mass combining the manpower and nature. On the irrigation works, it also belongs to " storage" facility, so usually called artificial lake or man-made lake.
The forming process of the man-made lakes is as the cartoon shows.
The forming process of a type of tectonic lakes-the rift lake is:
- an original river system. The river flows downwards, forming mainstream and tributary.
- the dyke is built at one section of the river course catering to the people's need.
- the dyke blocks up the river and the flowing water is accumulated.
- the accumulated water forms the anthropogenic lake --Reservoir.
Different from natural lakes, "Anthropogenic Lakes" have reflected the intelligence that the mankind utilizes and transforms the nature. The reservoir appears and develops in the process of mankind's fighting against floods and water preservation. As far back as more than 4000 years ago, in ancient Egypt and Mesopotamia, the people started to build reservoirs in the world in order to prevent floods and cater to the irrigation need. The Chinese people began to build up the irrigation projects early in the sixth century BC, and some projects are still functioning so far. According to the statistics, the total capacity of the reservoirs all around the world is up to 5500 km3, and the surface area exceeds 350,000 km2. In the early stage since the founding of the People's Republic of China, the first comprehensive project- Guanting Reservoir was built, aimed at controlling the flood and supplying water. By the end of 1950, there have already built up 86852 reservoirs around the country, with the total storage capacity accounting for 59% that of natural lakes, nearly 2 times of the freshwater lake storage amount.
Except the famous reservoirs in the ancient times -Shaopo Lake and Jianhu Lake, there is still a lake in the shape of reservoir-Hongze Lake. At the present, there has built a batch of reservoirs, such as Liujia Gorge, Yanguo Gorge, Bapan Gorge, Qingtong Gorge, Sanmen Gorge and Longping Gorge Reservoirs in the middle and upper reaches of the Yellow River; Danjiangkou, Zhexi, Wujiang, and Ertan Reservoirs in the middle and upper reaches of the Yangtze River. The Xin'anJiang Reservoir, namely Qiandao Lake, is a famous tourist zone in China. There is also the world-famous Three Gorges Project that is still being built, with the reservoir dam up to 180 meters, total storage 20 billion cubic meters, the installed capacity of the power station 13 million kilowatts, and an annual generated energy 65 billion kilowatt-hours . It can be rated as the first in the world.
Hongze Lake is the youngest lake in the five major freshwater lakes in China. Before the Tang Dynasty and Song Dynasty, there already exist some small-scale lakes at the lower reaches of Huaihe River. On their foundation, the reservoir type of lake finally took shape after the Yellow River moved to the south and pirated the Huaihe River in a long term as well as building dykes for preserving water.
The shape of Hongze Lake is like a flying hawk spreading its wings. The east bank is smooth and straight, but the rest strandline is zigzagging.
The climate in the lake district belongs to the transitional type between the northern subtropical zone and the south temperate zone. Obvious differences exist in the distribution of the water color and transparency of the lake water, which is generally influenced by the silt and stormy waves carried by the rivers at the open water area of the river mouth, therefore presenting a color of greenish-yellow. The local masses have a vivid description about the Hongze Lake, "a golden picture at the sunrise."
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